1. Field of the Invention
This invention relates to a novel class of steroids which are believed to bind to the progestin receptor and which exhibit potent antiprogestational activity. Such compounds are useful for treatment of fibroids, endometriosis, and certain tumors, in causing cervical ripening prior to delivery, in hormone replacement therapy and in control of fertility and reproduction.
2. Discussion of the Background
Progesterone plays a major role in reproductive health and functioning. Its effects on, for example, the uterus, breast, cervix and hypothalamic-pituitary unit are well established. It also has extra-reproductive activities that are less well studied, such as effects on the brain, the immune system, the vascular endothelial system and on lipid metabolism. Given this wide array of effects, it is apparent that compounds which mimic some of the effects of progesterone (agonists), antagonize these effects (antagonists) or exhibit mixed effects (partial agonists or mixed agonist/antagonist) can be useful in treating a variety of disease states and conditions.
Steroid hormones exert their effects, in-part, by binding to intracellular receptors. Compounds that bind to the appropriate receptors and are antagonists or partial agonists of the estrogenic and androgenic hormones have long been known, but it was not until around 1982 that the discovery of compounds that bind to the progesterone receptor and antagonize the effects of progesterone was announced. Since then, a number of such compounds have been reported in the scientific and patent literature and their effects in vitro, in animals and in humans have been studied. Although compounds such as estrogens and certain enzyme inhibitors can prevent the physiological effects of endogenous progesterone, in this discussion "antiprogestin" is confined to those compounds that bind to the progestin receptor.
Information indicating that antiprogestins would be effective in a number of medical conditions is now available. This information has been summarized in a report from the Institute of Medicine (Donaldson, Molly S.; Dorflinger, L.; Brown, Sarah S.; Benet, Leslie Z., Editors, Clinical Applications of Mifepristone (RU 486) and Other Antiprogestins, Committee on Antiprogestins: Assessing the Science, Institute of Medicine, National Academy Press, 1993). In view of the pivotal role that progesterone plays in reproduction, it is not surprising that antiprogestins could play a part in fertility control, including contraception (long-term and emergency or post-coital), menses induction and medical termination of pregnancy, but there are many other potential uses that have been supported by small clinical or preclinical studies. Among these are the following:
1. Labor and delivery--antiprogestins may be used for cervical ripening prior to labor induction such as at term or when labor must be induced due to fetal death. They may also be used to help induce labor in term or post-term pregnancies.
2. Treatment of uterine leiomyomas (fibroids)--these non-malignant tumors may affect up to 20% of women over 30 years old and are one of the most common reasons for surgery in women during their reproductive years. Hysterectomy, the common treatment for persistent symptoms, of course results in sterility.
3. Treatment of endometriosis--this common (5 to 15% incidence, much larger in infertile women) and often painful condition is now treated with drugs such as danazol or gonadotrophin-releasing hormone analogs that have significant side-effects, or must be dealt with surgically.
4. Hormone replacement therapy, where they may be given to interupt or curtail the activity of progestins.
5. Cancers, particularly breast cancers--the presence of progestin receptors in many breast cancers has suggested the use of antiprogestins in treating metatstatic cancer or in prevention of recurrence or initial development of cancer.
6. Other tumors such as meningiomas--these brain membrane tumors, although nonmalignant, result in death of the patient and nonsurgical treatments are lacking.
7. Male contraception--antiprogestins can interfere with sperm viability, although whether this is an antiprogestational effect or not is controversial, as it may relate to the antiglucocorticoid activity of such compounds.
8. Antiestrogenic effects--at least some antiprogestins oppose the action of estrogens in certain tests, but apparently through a mechanism that does not involve classical hormone receptors. This opens a variety of possibilities for their medical use.
9. Antiglucocorticoid effects--this is a common side-effect of antiprogestins, which can be useful in some instances, such as the treatment of Cushing's syndrome, and could play a role in immune disorders, for example. In other instances it is desirable to minimize such effects.
The effects and uses of progesterone agonists have been well documented. In addition, it has been recently shown that certain compounds structurally related to the known antiprogestins have strong agonist activity in certain biological systems (e.g., the classical progestin effects in the estrogen-primed immature rabbit uterus; cf. C. E. Cook et al., Life Sciences, 52, 155-162 (1993)). Such compounds are partial agonists in human cell-derived receptor systems, where they bind to a site distinct from both the progestin and antiprogestin sites (Wagner et al., Proc. Natl. Acad. Sci., 93, 8739-8744 (1996)). Thus the general class of antiprogestins can have subclasses, which may vary in their clinical profiles.
The earliest antiprogestins, in addition to having an 11.beta.-aryl substituent, were substituted with a 17.beta.-hydroxyl group and various 17.alpha.-substituents. (See for example, Teutsch, Jean G.; Costerousse, Germain; Philibert, Daniel, and Deraedt, Roger. Novel steroids. U.S. Pat. No. 4,386,085. 1983; Philibert, Daniel; Teutsch, Jean G.; Costerousse, Germain, and Deraedt, Roger. 3-Keto-19-nor-.DELTA.-4,9-steroids. U.S. Pat. No. 4,477,445. 1983; Teutsch, Jean G.; Pantin, Germain; Costerousse, Saint-Maurice; Daniel Philibert; La Varenne Saint Hilaire; Roger Deraedt, inventors. Steroid derivatives. Roussel Uclaf, assignee. U.S. Pat. No. 4,447,424. 1984; Cook, C. Edgar; Tallent, C. Ray; Reel, Jerry R., and Wani, Mansukh C. 17.alpha.-(Substituted-methyl)-17.beta.-hydroxy/esterified hydroxy steroids and pharmaceutical compositions containing them. U.S. Pat. No. 4,774,236 (1988) and 4,861,763 (1989)). Then it was discovered that a 17.beta.-acetyl, 17.alpha.-acyloxy group in the presence of 11.beta.-aryl could also generate compounds with antiprogestational effects (Cook, C. Edgar; Lee, Y.-W.; Reel, Jerry R.; Wani, Mansukh C., Rector, Douglas. 11.beta.-Substituted Progesterone Analogs. U.S. Pat. Nos. 4,954,490 (1990) and 5,073,548 (1991)), and various permutations of these findings have been made as well. However, introduction of a 16.alpha.-ethyl group or a hydrogen substituent at the 17.alpha.-position in the 17.beta.-acyl series of compounds is reported to lead to agonist or partial agonist activity (C. E. Cook et al., Life Sciences, 52, 155-162 (1993)).
Generally antiprogestational activity has been associated with the presence of an 11.beta.-aryl substituent on the steroid nucleus, together with a .DELTA..sup.4,9 -3-ketone or .DELTA..sup.4 -3-ketone moiety. However, it has been shown that substituents on the D-ring of the steroid can have a marked influence on the biological profile of these compounds (see above). Thus changes in the D-ring of the steroid result in a wide variety of effects on the biological activity.
It can be seen that the 17.beta.-position of current antiprogestins has been characterized by substitution with a carbon or an oxygen atom. No reports have been made of the effect of a nitro or nitro-related substituent such as a spironitrone at the 17.beta.-position in steroids bearing an 11.beta.-aryl substituent. This invention provides a group of novel 17.beta.-nitro steroids, which are characterized by 11.beta.-substitution, particularly 11.beta.-aryl substitution. Very few 17.beta.-nitro steroids and none with 11.beta.-substitution have been reported in either the general chemical literature or in patents. Cf. for example, Patchett, Arthur A.; Metuchen, Glen E.; Arth, Cranford, and Hoffman, Frances G. Alkanoylthio and pyrazolo androstane derivatives. U.S. Pat. No. 3,094,521, 1963. This patent describes a synthesis of 17-nitro steroids and their Michael reaction with methyl acrylate, but no biological activity was reported as associated with the nitro compounds.
In addition, this invention provides a group of novel 17,17-spiro cyclic nitrone steroids. Although a few 17,17-spiro cyclic nitrone steroids are known (cf. Keana, John F. W.; Tamura, Toshinari; McMillen, Debra A., and Jost, Patricia C. Synthesis and characterization of a novel cholesterol nitroxide spin label. Application to the molecular organization of human high-density lipoprotein. J. Am. Chem. Soc. 103: 4904-4912 (1981)), these were used to develop spin labels and not for their biological properties. No such compounds with 11.beta.-aryl substituents have been reported.
In spite of the clinical promise of antiprogestins, as of May 1, 1998, there were no antiprogestin drugs marketed in the United States or many other countries. Only one antiprogestin drug is approved and available for clinical use anywhere in the world and that drug, mifepristone, is mainly used for medical termination of pregnancy. A number of factors are the cause of this situation, but certainly a need exists for new antiprogestational drugs that can be used for the conditions described above. Accordingly there also remains a need for antiprogestin compounds which exhibit higher specificity.
It is therefore the purpose of the present invention to provide novel and potent progestin antagonists (antiprogestins) and mixed or partial progestin agonists, and to provide methods for their medical use in mammals, including humans.